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1
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Phan LT, Oh C, He T, Manavalan B. A comprehensive revisit of the machine-learning tools developed for the identification of enhancers in the human genome. Proteomics 2023; 23:e2200409. [PMID: 37021401 DOI: 10.1002/pmic.202200409] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2023] [Revised: 03/18/2023] [Accepted: 03/27/2023] [Indexed: 04/07/2023]
Abstract
Enhancers are non-coding DNA elements that play a crucial role in enhancing the transcription rate of a specific gene in the genome. Experiments for identifying enhancers can be restricted by their conditions and involve complicated, time-consuming, laborious, and costly steps. To overcome these challenges, computational platforms have been developed to complement experimental methods that enable high-throughput identification of enhancers. Over the last few years, the development of various enhancer computational tools has resulted in significant progress in predicting putative enhancers. Thus, researchers are now able to use a variety of strategies to enhance and advance enhancer study. In this review, an overview of machine learning (ML)-based prediction methods for enhancer identification and related databases has been provided. The existing enhancer-prediction methods have also been reviewed regarding their algorithms, feature selection processes, validation techniques, and software utility. In addition, the advantages and drawbacks of these ML approaches and guidelines for developing bioinformatic tools have been highlighted for a more efficient enhancer prediction. This review will serve as a useful resource for experimentalists in selecting the appropriate ML tool for their study, and for bioinformaticians in developing more accurate and advanced ML-based predictors.
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Affiliation(s)
- Le Thi Phan
- Computational Biology and Bioinformatics Laboratory, Department of Integrative Biotechnology, College of Biotechnology and Bioengineering, Sungkyunkwan University, Suwon, Gyeonggi-do, South Korea
| | - Changmin Oh
- Computational Biology and Bioinformatics Laboratory, Department of Integrative Biotechnology, College of Biotechnology and Bioengineering, Sungkyunkwan University, Suwon, Gyeonggi-do, South Korea
| | - Tao He
- Beidahuang Industry Group General Hospital, Harbin, China
| | - Balachandran Manavalan
- Computational Biology and Bioinformatics Laboratory, Department of Integrative Biotechnology, College of Biotechnology and Bioengineering, Sungkyunkwan University, Suwon, Gyeonggi-do, South Korea
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2
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Ray-Jones H, Spivakov M. Transcriptional enhancers and their communication with gene promoters. Cell Mol Life Sci 2021; 78:6453-6485. [PMID: 34414474 PMCID: PMC8558291 DOI: 10.1007/s00018-021-03903-w] [Citation(s) in RCA: 32] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2021] [Revised: 07/08/2021] [Accepted: 07/19/2021] [Indexed: 12/13/2022]
Abstract
Transcriptional enhancers play a key role in the initiation and maintenance of gene expression programmes, particularly in metazoa. How these elements control their target genes in the right place and time is one of the most pertinent questions in functional genomics, with wide implications for most areas of biology. Here, we synthesise classic and recent evidence on the regulatory logic of enhancers, including the principles of enhancer organisation, factors that facilitate and delimit enhancer-promoter communication, and the joint effects of multiple enhancers. We show how modern approaches building on classic insights have begun to unravel the complexity of enhancer-promoter relationships, paving the way towards a quantitative understanding of gene control.
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Affiliation(s)
- Helen Ray-Jones
- MRC London Institute of Medical Sciences, London, W12 0NN, UK
- Institute of Clinical Sciences, Faculty of Medicine, Imperial College, London, W12 0NN, UK
| | - Mikhail Spivakov
- MRC London Institute of Medical Sciences, London, W12 0NN, UK.
- Institute of Clinical Sciences, Faculty of Medicine, Imperial College, London, W12 0NN, UK.
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3
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Thiecke MJ, Wutz G, Muhar M, Tang W, Bevan S, Malysheva V, Stocsits R, Neumann T, Zuber J, Fraser P, Schoenfelder S, Peters JM, Spivakov M. Cohesin-Dependent and -Independent Mechanisms Mediate Chromosomal Contacts between Promoters and Enhancers. Cell Rep 2020; 32:107929. [PMID: 32698000 PMCID: PMC7383238 DOI: 10.1016/j.celrep.2020.107929] [Citation(s) in RCA: 110] [Impact Index Per Article: 22.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2020] [Revised: 06/01/2020] [Accepted: 06/29/2020] [Indexed: 12/20/2022] Open
Abstract
It is currently assumed that 3D chromosomal organization plays a central role in transcriptional control. However, depletion of cohesin and CTCF affects the steady-state levels of only a minority of transcripts. Here, we use high-resolution Capture Hi-C to interrogate the dynamics of chromosomal contacts of all annotated human gene promoters upon degradation of cohesin and CTCF. We show that a majority of promoter-anchored contacts are lost in these conditions, but many contacts with distinct properties are maintained, and some new ones are gained. The rewiring of contacts between promoters and active enhancers upon cohesin degradation associates with rapid changes in target gene transcription as detected by SLAM sequencing (SLAM-seq). These results provide a mechanistic explanation for the limited, but consistent, effects of cohesin and CTCF depletion on steady-state transcription and suggest the existence of both cohesin-dependent and -independent mechanisms of enhancer-promoter pairing.
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Affiliation(s)
- Michiel J Thiecke
- Nuclear Dynamics Programme, Babraham Institute, Cambridge CB22 3AT, UK
| | - Gordana Wutz
- Research Institute of Molecular Pathology, Vienna Biocenter, Vienna 1030, Austria
| | - Matthias Muhar
- Research Institute of Molecular Pathology, Vienna Biocenter, Vienna 1030, Austria
| | - Wen Tang
- Research Institute of Molecular Pathology, Vienna Biocenter, Vienna 1030, Austria
| | - Stephen Bevan
- Nuclear Dynamics Programme, Babraham Institute, Cambridge CB22 3AT, UK; Epigenetics Programme, Babraham Institute, Cambridge CB22 3AT, UK
| | - Valeriya Malysheva
- Nuclear Dynamics Programme, Babraham Institute, Cambridge CB22 3AT, UK; MRC London Institute of Medical Sciences, London W12 0NN, UK; Institute of Clinical Sciences, Faculty of Medicine, Imperial College, London W12 0NN, UK
| | - Roman Stocsits
- Research Institute of Molecular Pathology, Vienna Biocenter, Vienna 1030, Austria
| | - Tobias Neumann
- Research Institute of Molecular Pathology, Vienna Biocenter, Vienna 1030, Austria
| | - Johannes Zuber
- Research Institute of Molecular Pathology, Vienna Biocenter, Vienna 1030, Austria
| | - Peter Fraser
- Nuclear Dynamics Programme, Babraham Institute, Cambridge CB22 3AT, UK; Department of Biological Science, Florida State University, Tallahassee, FL 32301, USA
| | - Stefan Schoenfelder
- Nuclear Dynamics Programme, Babraham Institute, Cambridge CB22 3AT, UK; Epigenetics Programme, Babraham Institute, Cambridge CB22 3AT, UK
| | - Jan-Michael Peters
- Research Institute of Molecular Pathology, Vienna Biocenter, Vienna 1030, Austria
| | - Mikhail Spivakov
- Nuclear Dynamics Programme, Babraham Institute, Cambridge CB22 3AT, UK; MRC London Institute of Medical Sciences, London W12 0NN, UK; Institute of Clinical Sciences, Faculty of Medicine, Imperial College, London W12 0NN, UK.
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4
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Charting the cis-regulome of activated B cells by coupling structural and functional genomics. Nat Immunol 2019; 21:210-220. [PMID: 31873292 DOI: 10.1038/s41590-019-0565-0] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2019] [Accepted: 11/18/2019] [Indexed: 12/25/2022]
Abstract
Cis-regulomes underlying immune-cell-specific genomic states have been extensively analyzed by structure-based chromatin profiling. By coupling such approaches with a high-throughput enhancer screen (self-transcribing active regulatory region sequencing (STARR-seq)), we assembled a functional cis-regulome for lipopolysaccharide-activated B cells. Functional enhancers, in contrast with accessible chromatin regions that lack enhancer activity, were enriched for enhancer RNAs (eRNAs) and preferentially interacted in vivo with B cell lineage-determining transcription factors. Interestingly, preferential combinatorial binding by these transcription factors was not associated with differential enrichment of their sites. Instead, active enhancers were resolved by principal component analysis (PCA) from all accessible regions by co-varying transcription factor motif scores involving a distinct set of signaling-induced transcription factors. High-resolution chromosome conformation capture (Hi-C) analysis revealed multiplex, activated enhancer-promoter configurations encompassing numerous multi-enhancer genes and multi-genic enhancers engaged in the control of divergent molecular pathways. Motif analysis of pathway-specific enhancers provides a catalog of diverse transcription factor codes for biological processes encompassing B cell activation, cycling and differentiation.
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5
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Vernimmen D, Bickmore WA. The Hierarchy of Transcriptional Activation: From Enhancer to Promoter. Trends Genet 2016; 31:696-708. [PMID: 26599498 DOI: 10.1016/j.tig.2015.10.004] [Citation(s) in RCA: 94] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2015] [Revised: 09/18/2015] [Accepted: 10/15/2015] [Indexed: 12/20/2022]
Abstract
Regulatory elements (enhancers) that are remote from promoters play a critical role in the spatial, temporal, and physiological control of gene expression. Studies on specific loci, together with genome-wide approaches, suggest that there may be many common mechanisms involved in enhancer-promoter communication. Here, we discuss the multiprotein complexes that are recruited to enhancers and the hierarchy of events taking place between regulatory elements and promoters.
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Affiliation(s)
- Douglas Vernimmen
- The Roslin Institute, Developmental Biology Division, University of Edinburgh, Easter Bush, Midlothian EH25 9RG, UK.
| | - Wendy A Bickmore
- MRC Human Genetics Unit, Institute of Genetics and Molecular Medicine, University of Edinburgh, Edinburgh EH4 2XU, UK
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6
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Smith SM, Carew NT, Milcarek C. RNA polymerases in plasma cells trav-ELL2 the beat of a different drum. World J Immunol 2015; 5:99-112. [DOI: 10.5411/wji.v5.i3.99] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/26/2015] [Revised: 08/19/2015] [Accepted: 11/17/2015] [Indexed: 02/05/2023] Open
Abstract
There is a major transformation in gene expression between mature B cells (including follicular, marginal zone, and germinal center cells) and antibody secreting cells (ASCs), i.e., ASCs, (including plasma blasts, splenic plasma cells, and long-lived bone marrow plasma cells). This significant change-over occurs to accommodate the massive amount of secretory-specific immunoglobulin that ASCs make and the export processes itself. It is well known that there is an up-regulation of a small number of ASC-specific transcription factors Prdm1 (B-lymphocyte-induced maturation protein 1), interferon regulatory factor 4, and Xbp1, and the reciprocal down-regulation of Pax5, Bcl6 and Bach2, which maintain the B cell program. Less well appreciated are the major alterations in transcription elongation and RNA processing occurring between B cells and ASCs. The three ELL family members ELL1, 2 and 3 have different protein sequences and potentially distinct cellular roles in transcription elongation. ELL1 is involved in DNA repair and small RNAs while ELL3 was previously described as either testis or stem-cell specific. After B cell stimulation to ASCs, ELL3 levels fall precipitously while ELL1 falls off slightly. ELL2 is induced at least 10-fold in ASCs relative to B cells. All of these changes cause the RNA Polymerase II in ASCs to acquire different properties, leading to differences in RNA processing and histone modifications.
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7
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Fyon F, Cailleau A, Lenormand T. Enhancer Runaway and the Evolution of Diploid Gene Expression. PLoS Genet 2015; 11:e1005665. [PMID: 26561855 PMCID: PMC4642963 DOI: 10.1371/journal.pgen.1005665] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2015] [Accepted: 10/22/2015] [Indexed: 11/18/2022] Open
Abstract
Evidence is mounting that the evolution of gene expression plays a major role in adaptation and speciation. Understanding the evolution of gene regulatory regions is indeed an essential step in linking genotypes and phenotypes and in understanding the molecular mechanisms underlying evolutionary change. The common view is that expression traits (protein folding, expression timing, tissue localization and concentration) are under natural selection at the individual level. Here, we use a theoretical approach to show that, in addition, in diploid organisms, enhancer strength (i.e., the ability of enhancers to activate transcription) may increase in a runaway process due to competition for expression between homologous enhancer alleles. These alleles may be viewed as self-promoting genetic elements, as they spread without conferring a benefit at the individual level. They gain a selective advantage by getting associated to better genetic backgrounds: deleterious mutations are more efficiently purged when linked to stronger enhancers. This process, which has been entirely overlooked so far, may help understand the observed overrepresentation of cis-acting regulatory changes in between-species phenotypic differences, and sheds a new light on investigating the contribution of gene expression evolution to adaptation. With the advent of new sequencing technologies, the evolution of gene expression regulation is becoming a subject of intensive research. In this paper, we report an entirely new phenomenon acting on the evolution of gene regulatory sequences. We show that in a small genomic region around genes there is a selection pressure to increase expression, such that stronger enhancers are favored. This leads to an open-ended escalation of enhancer strength. This outcome is not a particular case and we expect it to occur for all genes in nearly all eukaryotic diploid organisms. We also show that this escalation is not stopped by stabilizing selection on expression profiles. Indeed, regulators may coevolve to maintain optimal phenotypes despite the enhancer strength escalation. This widespread phenomenon can significantly shift our understanding of gene regulatory regions and opens a wide array of possible tests.
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Affiliation(s)
- Frédéric Fyon
- UMR 5175 CEFE, CNRS, Université Montpellier, Université P. Valéry, EPHE, Montpellier, France
- * E-mail:
| | - Aurélie Cailleau
- UMR 5175 CEFE, CNRS, Université Montpellier, Université P. Valéry, EPHE, Montpellier, France
| | - Thomas Lenormand
- UMR 5175 CEFE, CNRS, Université Montpellier, Université P. Valéry, EPHE, Montpellier, France
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8
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Abstract
Over the last three decades, studies of the α- and β-globin genes clusters have led to elucidation of the general principles of mammalian gene regulation, such as RNA stability, termination of transcription, and, more importantly, the identification of remote regulatory elements. More recently, detailed studies of α-globin regulation, using both mouse and human loci, allowed the dissection of the sequential order in which transcription factors are recruited to the locus during lineage specification. These studies demonstrated the importance of the remote regulatory elements in the recruitment of RNA polymerase II (PolII) together with their role in the generation of intrachromosomal loops within the locus and the removal of polycomb complexes during differentiation. The multiple roles attributed to remote regulatory elements that have emerged from these studies will be discussed.
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Affiliation(s)
- Douglas Vernimmen
- The Roslin Institute, Developmental Biology Division, University of Edinburgh, Easter Bush, Midlothian, United Kingdom
- * E-mail:
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9
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Kasper LH, Qu C, Obenauer JC, McGoldrick DJ, Brindle PK. Genome-wide and single-cell analyses reveal a context dependent relationship between CBP recruitment and gene expression. Nucleic Acids Res 2014; 42:11363-82. [PMID: 25249627 PMCID: PMC4191404 DOI: 10.1093/nar/gku827] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2014] [Revised: 08/27/2014] [Accepted: 09/01/2014] [Indexed: 12/31/2022] Open
Abstract
Genome-wide distribution of histone H3K18 and H3K27 acetyltransferases, CBP (CREBBP) and p300 (EP300), is used to map enhancers and promoters, but whether these elements functionally require CBP/p300 remains largely uncertain. Here we compared global CBP recruitment with gene expression in wild-type and CBP/p300 double-knockout (dKO) fibroblasts. ChIP-seq using CBP-null cells as a control revealed nearby CBP recruitment for 20% of constitutively-expressed genes, but surprisingly, three-quarters of these genes were unaffected or slightly activated in dKO cells. Computationally defined enhancer-promoter-units (EPUs) having a CBP peak near the enhancer-like element were more predictive, with CBP/p300 deletion attenuating expression of 40% of such constitutively-expressed genes. Examining signal-responsive (Hypoxia Inducible Factor) genes showed that 97% were within 50 kilobases of an inducible CBP peak, and 70% of these required CBP/p300 for full induction. Unexpectedly, most inducible CBP peaks occurred near signal-nonresponsive genes. Finally, single-cell expression analysis revealed additional context dependence where some signal-responsive genes were not uniformly dependent on CBP/p300 in individual cells. While CBP/p300 was needed for full induction of some genes in single-cells, for other genes CBP/p300 increased the probability of maximal expression. Thus, target gene context influences the transcriptional requirement for CBP/p300, possibly by multiple mechanisms.
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Affiliation(s)
- Lawryn H Kasper
- Department of Biochemistry, St Jude Children's Research Hospital, 262 Danny Thomas Place, Memphis, TN 38105, USA
| | - Chunxu Qu
- Department of Computational Biology, St Jude Children's Research Hospital, 262 Danny Thomas Place, Memphis, TN 38105, USA
| | - John C Obenauer
- Department of Computational Biology, St Jude Children's Research Hospital, 262 Danny Thomas Place, Memphis, TN 38105, USA
| | - Daniel J McGoldrick
- Department of Computational Biology, St Jude Children's Research Hospital, 262 Danny Thomas Place, Memphis, TN 38105, USA
| | - Paul K Brindle
- Department of Biochemistry, St Jude Children's Research Hospital, 262 Danny Thomas Place, Memphis, TN 38105, USA
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10
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Loss of an Igκ gene enhancer in mature B cells results in rapid gene silencing and partial reversible dedifferentiation. Mol Cell Biol 2013; 33:2091-101. [PMID: 23508106 DOI: 10.1128/mcb.01569-12] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
We address here whether there is cellular memory of a transcriptional enhancer once it has served its purpose to establish an active chromatin state. We have previously shown that the mouse Igκ gene's downstream enhancers, E3' and Ed, are essential but play redundant roles for establishing transcriptional activity in the locus during B cell development. To determine whether these enhancers are also necessary for the maintenance of transcriptional activity, we conditionally deleted E3' in mature B cells that possessed Ed(-/-) alleles. Upon E3' deletion, the locus became rapidly silenced and lost positive histone epigenetic marks, and the mature B cells partially dedifferentiated, induced RAG-1 and -2 along with certain other pro-B cell makers, and then redifferentiated after triggering Igλ gene rearrangements. We conclude that the Igκ gene's downstream enhancers are essential for both the establishment and maintenance of transcriptional activity and that there is no cellular memory of previous transcriptional activity in this locus. Furthermore, upon enhancer loss, the mature B cells unexpectedly underwent reversible retrograde differentiation. This result establishes that receptor editing can occur in mature B cells and raises the possibility that this may provide a tolerance mechanism for eliminating autoreactive B cells in the periphery.
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11
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Wan M, Gu H, Wang J, Huang H, Zhao J, Kaundal RK, Yu M, Kushwaha R, Chaiyachati BH, Deerhake E, Chi T. Inducible mouse models illuminate parameters influencing epigenetic inheritance. Development 2013; 140:843-52. [PMID: 23325759 DOI: 10.1242/dev.088229] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Environmental factors can stably perturb the epigenome of exposed individuals and even that of their offspring, but the pleiotropic effects of these factors have posed a challenge for understanding the determinants of mitotic or transgenerational inheritance of the epigenetic perturbation. To tackle this problem, we manipulated the epigenetic states of various target genes using a tetracycline-dependent transcription factor. Remarkably, transient manipulation at appropriate times during embryogenesis led to aberrant epigenetic modifications in the ensuing adults regardless of the modification patterns, target gene sequences or locations, and despite lineage-specific epigenetic programming that could reverse the epigenetic perturbation, thus revealing extraordinary malleability of the fetal epigenome, which has implications for 'metastable epialleles'. However, strong transgenerational inheritance of these perturbations was observed only at transgenes integrated at the Col1a1 locus, where both activating and repressive chromatin modifications were heritable for multiple generations; such a locus is unprecedented. Thus, in our inducible animal models, mitotic inheritance of epigenetic perturbation seems critically dependent on the timing of the perturbation, whereas transgenerational inheritance additionally depends on the location of the perturbation. In contrast, other parameters examined, particularly the chromatin modification pattern and DNA sequence, appear irrelevant.
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Affiliation(s)
- Mimi Wan
- Department of Immunobiology, Yale University, New Haven, CT 06520, USA
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12
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Block DHS, Hussein R, Liang LW, Lim HN. Regulatory consequences of gene translocation in bacteria. Nucleic Acids Res 2012; 40:8979-92. [PMID: 22833608 PMCID: PMC3467084 DOI: 10.1093/nar/gks694] [Citation(s) in RCA: 77] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Gene translocations play an important role in the plasticity and evolution of bacterial genomes. In this study, we investigated the impact on gene regulation of three genome organizational features that can be altered by translocations: (i) chromosome position; (ii) gene orientation; and (iii) the distance between a target gene and its transcription factor gene (‘target-TF distance’). Specifically, we quantified the effect of these features on constitutive expression, transcription factor binding and/or gene expression noise using a synthetic network in Escherichia coli composed of a transcription factor (LacI repressor) and its target gene (yfp). Here we show that gene regulation is generally robust to changes in chromosome position, gene orientation and target-TF distance. The only demonstrable effect was that chromosome position alters constitutive expression, due to changes in gene copy number and local sequence effects, and that this determines maximum and minimum expression levels. The results were incorporated into a mathematical model which was used to quantitatively predict the responses of a simple gene network to gene translocations; the predictions were confirmed experimentally. In summary, gene translocation can modulate constitutive gene expression levels due to changes in chromosome position but it has minimal impact on other facets of gene regulation.
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Affiliation(s)
- Dena H S Block
- Department of Integrative Biology, 1005 Valley Life Sciences Building MC 3140, University of California, Berkeley, CA 94720-3140, USA
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13
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Xiong Y, Bosselut R. CD4-CD8 differentiation in the thymus: connecting circuits and building memories. Curr Opin Immunol 2012; 24:139-45. [PMID: 22387323 PMCID: PMC3773541 DOI: 10.1016/j.coi.2012.02.002] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2011] [Revised: 01/22/2012] [Accepted: 02/06/2012] [Indexed: 10/28/2022]
Abstract
The proper choice of the CD4-helper or CD8-cytotoxic lineages by developing T cells is crucial for the generation of an antigen-responsive and functionally fit T cell repertoire. Here we present a brief overview of the transcriptional control of this process, with emphasis on two issues. The study of Cd4 expression, that had previously generated important paradigms for transcriptional regulation in eukaryotic cells, now brings new twists to the concept of 'epigenetic memory'. And connections are emerging between transcriptional regulators critical for commitment to either lineage. The present review attempts to integrate these findings and discusses the still elusive mechanisms that match CD4-CD8 lineage differentiation to MHC specificity.
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Affiliation(s)
- Yumei Xiong
- Laboratory of Immune Cell Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD, USA
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14
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Fedoseeva DM, Kretova OV, Tchurikov NA. Molecular analysis of enhancer RNAs and chromatin modifications in the region of their synthesis in Drosophila cells possessing genetic constructs. DOKL BIOCHEM BIOPHYS 2012; 442:7-11. [PMID: 22419084 DOI: 10.1134/s1607672912010012] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2011] [Indexed: 11/22/2022]
Affiliation(s)
- D M Fedoseeva
- Engelhardt Institute of Molecular Biology, Russian Academy of Sciences, ul. Vavilova 32, Moscow, 119991, Russia
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15
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Raab JR, Chiu J, Zhu J, Katzman S, Kurukuti S, Wade PA, Haussler D, Kamakaka RT. Human tRNA genes function as chromatin insulators. EMBO J 2011; 31:330-50. [PMID: 22085927 DOI: 10.1038/emboj.2011.406] [Citation(s) in RCA: 102] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2011] [Accepted: 10/07/2011] [Indexed: 11/09/2022] Open
Abstract
Insulators help separate active chromatin domains from silenced ones. In yeast, gene promoters act as insulators to block the spread of Sir and HP1 mediated silencing while in metazoans most insulators are multipartite autonomous entities. tDNAs are repetitive sequences dispersed throughout the human genome and we now show that some of these tDNAs can function as insulators in human cells. Using computational methods, we identified putative human tDNA insulators. Using silencer blocking, transgene protection and repressor blocking assays we show that some of these tDNA-containing fragments can function as barrier insulators in human cells. We find that these elements also have the ability to block enhancers from activating RNA pol II transcribed promoters. Characterization of a putative tDNA insulator in human cells reveals that the site possesses chromatin signatures similar to those observed at other better-characterized eukaryotic insulators. Enhanced 4C analysis demonstrates that the tDNA insulator makes long-range chromatin contacts with other tDNAs and ETC sites but not with intervening or flanking RNA pol II transcribed genes.
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Affiliation(s)
- Jesse R Raab
- Department of MCD Biology, University of California, Santa Cruz, CA, USA
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16
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Roy AL, Sen R, Roeder RG. Enhancer-promoter communication and transcriptional regulation of Igh. Trends Immunol 2011; 32:532-9. [PMID: 21855411 DOI: 10.1016/j.it.2011.06.012] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2011] [Revised: 06/23/2011] [Accepted: 06/23/2011] [Indexed: 12/18/2022]
Abstract
Transcriptional regulation of eukaryotic protein-coding genes requires the participation of site-specific transcription factors that bind distal regulatory elements, as well as factors that, together with RNA polymerase II, form the basal transcription machinery at the core promoter. Gene regulation requires proper communication between promoters and enhancers, often over great distances. Therefore, it is important to understand the potentially inter-related transcription factor interactions at both of these elements. How this is achieved on tissue-specific genes, such as the immunoglobulin heavy chain (IgH) in B cells remains unclear. Here, we review known interactions at the Igh variable region (V(H)) promoters and present our perspective on promoter-enhancer interactions that are likely important for Ig gene regulation in B cells.
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Affiliation(s)
- Ananda L Roy
- Program in Immunology, Department of Pathology, Tufts University School of Medicine, Boston, MA, USA.
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17
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Milcarek C, Albring M, Langer C, Park KS. The eleven-nineteen lysine-rich leukemia gene (ELL2) influences the histone H3 protein modifications accompanying the shift to secretory immunoglobulin heavy chain mRNA production. J Biol Chem 2011; 286:33795-803. [PMID: 21832080 DOI: 10.1074/jbc.m111.272096] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
In plasma cells, immunoglobulin heavy chain (IgH) secretory-specific mRNA is made in high abundance as a result of both increased promoter proximal poly(A) site choice and weak splice-site skipping. Ell2, the eleven-nineteen lysine rich leukemia gene, is a transcription elongation factor that is induced ∼6-fold in plasma cells and has been shown to drive secretory-specific mRNA production. Reducing ELL2 by siRNA, which reduced processing to the secretion-specific poly(A) site, also influenced the methylations of histone H3K4 and H3K79 on the IgH gene and impacted positive transcription factor b (pTEFb), Ser-2 carboxyl-terminal phosphorylation, and polyadenylation factor additions to RNA polymerase II. The multiple lineage leukemia gene (MLL) and Dot1L associations with the IgH gene were also impaired in the absence of ELL2. To investigate the link between histone modifications, transcription elongation, and alternative RNA processing in IgH mRNA production, we performed chromatin immunoprecipitation on cultured mouse B and plasma cells bearing the identical IgH γ2a gene. In the plasma cells, as compared with the B cells, the H3K4 and H3K79 methylations extended farther downstream, past the IgH enhancer to the end of the transcribed region. Thus the downstream H3K4 and H3K79 methylation of the IgH associated chromatin in plasma cells is associated with increased polyadenylation and exon skipping, resulting from the actions of ELL2 transcription elongation factor.
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Affiliation(s)
- Christine Milcarek
- Department of Immunology, School of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania 15261, USA.
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Fedoseeva DM, Kretova OV, Tchurikov NA. Molecular analysis of RNA induced by enhancer in Drosophila cells carrying reporter genetic constructs. DOKL BIOCHEM BIOPHYS 2010; 435:339-43. [PMID: 21184308 DOI: 10.1134/s1607672910060153] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2010] [Indexed: 11/23/2022]
Affiliation(s)
- D M Fedoseeva
- Engelhardt Institute of Molecular Biology, Russian Academy of Sciences, ul. Vavilova 32, Moscow 119991, Russia
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Zhou X, Xiang Y, Garrard WT. The Igκ gene enhancers, E3' and Ed, are essential for triggering transcription. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 2010; 185:7544-52. [PMID: 21076060 PMCID: PMC3059262 DOI: 10.4049/jimmunol.1002665] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
The mouse Igκ gene locus has three known transcriptional enhancers: an intronic enhancer (Ei), a 3' enhancer (E3'), and a further downstream enhancer (Ed). Previous studies on B lymphocytes derived from mutant embryonic stem cells have shown that deletion of either Ei or E3' significantly reduces Igκ gene rearrangement, whereas the combined deletion of both Ei and E3' eliminates such recombination. Furthermore, deletion of either E3' or Ed significantly reduces rearranged Igκ gene transcription. To determine whether the combined presence of both E3' and Ed are essential for Igκ gene expression, we generated homozygous double knockout (DKO) mice with targeted deletions in both elements. Significantly, homozygous DKO mice were unable to generate κ(+) B cells both in bone marrow and the periphery and exhibited surface expression almost exclusively of Igλ-chains, despite the fact that they possessed potentially functional rearranged Igκ genes. Compared with their single-enhancer-deleted counterparts, Igκ loci in homozygous DKO mice exhibited dramatically reduced germline and rearranged gene transcription, lower levels of gene rearrangement and histone H3 acetylation, and markedly increased DNA methylation. This contributed to a partial developmental block at the pre-B cell stage of development. We conclude that the two downstream enhancers are essential in Igκ gene expression and that Ei in homozygous DKO mice is incapable of triggering Igκ gene transcription. Furthermore, these results reveal unexpected compensatory roles for Ed in E3' knockout mice in triggering germline transcription and Vκ gene rearrangements to both Jκ and RS elements.
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Affiliation(s)
- Xiaorong Zhou
- Department of Molecular Biology, University of Texas Southwestern Medical Center, 5323 Harry Hines Blvd., Dallas, TX 75390-9148
- Department of Microbiology and Immunology, Medical School of Nantong University, 19 Qixiu Road, Nantong, Jiangsu 226001, PR China
| | - Yougui Xiang
- Department of Molecular Biology, University of Texas Southwestern Medical Center, 5323 Harry Hines Blvd., Dallas, TX 75390-9148
| | - William T. Garrard
- Department of Molecular Biology, University of Texas Southwestern Medical Center, 5323 Harry Hines Blvd., Dallas, TX 75390-9148
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